Two-thirds of Americans say the war in Afghanistan hasn't been worth fighting, but 55 percent nonetheless favor keeping some U.S. forces there for training and counterinsurgency purposes, a new ABC News/Washington Post poll has found.

Public support for a smaller but continued U.S. military presence is steady despite the current controversy over a bilateral security agreement between the United States and Afghanistan, whose president, Hamid Karzai, has balked at signing a negotiated accord.

See PDF with full results, charts and tables here.

Overall, considering its costs to the United States vs. its benefits, 66 percent of Americans say the war has not been worth fighting, just one point from its high in July and matching peak criticism of the war in Iraq. Moreover, a new high of 50 percent feel "strongly" that the war in Afghanistan has not been worth it, outnumbering their opposites by 34 percentage points.

Still, Americans by 55-41 percent favor keeping some U.S. forces in place for training and counterinsurgency rather than the "zero option" of complete withdrawal in the year ahead. Those views are nearly identical to their levels in July.

An agreement for U.S. forces to stay beyond the 2014 withdrawal deadline was approved by a council of Afghan elders last month, but hit an impasse when Karzai added conditions and suggested that a pact should not be signed until after the Afghan presidential elections in April. U.S. officials have said an agreement needs to be signed by the end of this month.

This poll, produced for ABC by Langer Research Associates, finds that attitudes on the war overall influence views on withdrawal. Among Americans who think the war's been worth fighting, 76 percent support keeping some U.S. forces there. That falls to 47 percent among those who say it's not been worth fighting, including 41 percent of those who feel that way strongly.

Criticism of the war is substantial across demographic groups. Majorities of Republicans (54 percent) and conservatives (61 percent) say that given its costs vs. its benefits it has not been worth fighting, rising to 71 and 78 percent of independents and liberals, and including 67 percent of Democrats.

While most overall say some U.S. forces should remain beyond 2014, there are divisions in some disparate groups. Sixty-five percent of political moderates say some forces should remain; that falls among conservatives and liberals alike, to 52 and 46 percent, respectively.

METHODOLOGY - This ABC News/Washington Post poll was conducted by telephone Dec. 12-15, 2013, in English and Spanish, among a random national sample of 1,005 adults, including landline and cell-phone-only respondents. Results have a margin of sampling error of 3.5 points, including design effect. The survey was produced for ABC News by Langer Research Associates of New York, N.Y., with sampling, data collection and tabulation by Abt-SRBI of New York, N.Y.